Field of the Invention
The present invention relates to electronic communication and, more particularly, to facsimile communication.
Description of the Related Art
Traditionally, fax (short for facsimile) is the telephonic transmission of scanned printed material (both text and images). The original document is scanned into a fax machine and the contents are processed as a single fixed graphic image that is converted into a bitmap, which is then transmitted through the telephone system. A receiving fax machine converts the coded image before printing a paper copy. Originally, the scanned data was transmitted using an analog signal, but now, the data is more commonly transmitted via a digital signal. A fax can also be sent over IP (Facsimile over Internet Protocol (FoIP)), where a digitalized image is sent over an IP network using JPEG compression. More recently, a fax can be sent and received without using a traditional physical fax. For example, a fax can be sent and received via a personal computer using computer software or an internet fax service.
The capabilities of a fax machine can be categorized based on several indicators, such as group, class, data transmission rate, and conformance with ITU-T recommendations. The International Telecommunications Union (ITU) is an international standards body for telecommunications. Specifically, the ITU Telecommunication Standardization Sector (ITU-T) publishes different recommendations for the transmission of fax over a network. For example, T.30 is an ITU recommendation that specifies the session management procedures that support the establishment of a fax transmission, and T.38 is an ITU recommendation for allowing the transmission of fax over IP networks in real time.
The ITU also publishes fax protocols. For example, Group 3 protocol, first published in 1980, specifies the switched analog network and is an all-digital procedure. In addition, Group 3 allows two stations to agree on such things as transmission speed and page size. Further, the Group 3 protocol may be specified in several standards, such as T.4 and T.6, which specify the image transfer protocols and T.30. Facsimile protocols do not describe a specific implementation; therefore, different vendors have slightly different implementations of a fax protocol resulting in some fax devices having more difficulty with one type of fax board or soft fax than another.